25 Important Data Warehouse Interview Questions

Introduction

If you’re going to give the interview for the ‘Data Warehouse Analyst’ job in the Business Intelligence field, you must crack some basic to difficult questions related to Data Warehouse. So, you have to prepare for such questions by studying and learning new information related to this field. 

A Data Warehouse Analyst collects and manages data which is helpful to know prominent insights related to any business. That’s why the analyst is important to any business which wants to grow ahead to their competitors in the market. To acquire relevant results, the Data analyst must be responsible for the particular company’s data collection.  

To become successful in the interviews, you need to learn data warehouse interview questions as follows: 

Data Warehouse Concepts Interview Questions

What is Data Warehouse?

A Data Warehouse refers to the vast database of data from multiple sources within the company collected for a specific company or business to bring good results by bringing good changes in their business decisions. 

What is subject Oriented Data Warehouse?

The subject-oriented data warehouse means the collection of data for a particular area like product, client, or sales.

Data Warehousing and Data Mining Important Questions

Define the concept of Data Mining

Data mining means the analysis of big data for taking notes of useful perspectives like trends, themes, and patterns. 

What is Meta Data?

Metadata provides useful information within a set of data about other data. 

What is active data warehousing?

Active Data Warehousing captures and reposits the transactional data. By this system, the company can understand trends, patterns, and customers and make future decisions for the company’s image. 

What Does XMLA Mean?

XMLA as XML for analysis. It is a worthwhile system for acquiring data from OLAP. data mining, and from other multiple online sources.   XMLA is a simple object access protocol. The protocol uses two methods- Discover and Execute.  The discovery system collects the data from the internet while the execute system lets you implement applications against data sources.

Difference between Olap and Data Warehouse

What is OLAP?

OLAP refers to Online Analytical Process used to manage, process, and collect multi-dimensional data for management and analysis.

What is OLTP?

OLTP refers to Online Transaction Processing related to transaction-oriented data. It inserts, updates, and deletes a small amount of data in the database by using applications. It refers to transactions from users.

What is the difference between OLAP and OLTP data?

The difference between OLAP and OLTP data warehouse is a process of these two methods. OLAP consolidates data acquired from different sources while in OLTP, it processes real-time transaction data from users by inserting, updating, and deleting them in the small amount of data using applications.

Data Warehouse Questions and Answers for Experienced

Define ODS 

ODS means Operational data store which collects the latest data transactions from multiple operational sources or further operations over data and reporting. 

What is the Junk Dimension?

Junk Dimension is the single dimension used for storing the small dimension named junk attributes.  In this process, the junk attributes are a group of flags and text attributes that transmit them into a separate sub-dimension called junk dimension. 

What is SCD?

SCD refers to slowly changing dimensions. In these dimensions, the changes in the data happen slowly.

What are the types of SCD?

There are three types of SCD, as follows:

SCD1: The new record takes the place of the original record

SCD2:  The new record adds in the dimension table

SCD3: New data enters by changing the original data 

Advanced-Data Warehouse Interview Questions 

What is the difference between a data warehouse and a data mart?

The Data warehouse is the large storage of the data collected from multiple sources within an organization. While the data mart works as a subset of a data warehouse collects the data of a particular department/field in the business.

Talking about size, data mart has a small size of less than 100GB and a simple design.   On the other hand, the data warehouse comes with a complex design and takes up more than 100GB.

Define VLDB?

VLDB is a Very Large Database consisting of a one terabyte database. The database needs a large number of database rows and the storage space with the largest file. This database uses transaction processing applications and decision support applications for a large number of users.

What is Star Schema?

In Star Schema, the tables are organized in such a way so that the result can be acquired instantly in the database environment.

What is BUS Schema?

The BUS Schema refers to the suite of facts with standardized description and confirmed dimension.

Define Snowflake Schema?

Snowflake Schema is a primary dimension table interlinked with other tables.  It can be joined with the fact table.

Data Warehouse Interview Questions for ETL Developer

What is ETL?

ETL means Extract, Transform, and Load.  The system is used to collect data from different sources and consolidate it into the centre location.

How does ETL use tools?

There are various tools to extract, transform, and load the data such as Data Stage, Oracle, Informatica, Ab Initio, Warehouse Builder, and Data Junction.

Data Warehouse Architecture Interview Questions

What is the 3-layer architecture of the ETL cycle?

• Staging Layer – Keeps the data acquired from sources. 
• Data Integration Layer – Transfers the data acquired from the staging layer into the database.  The data can be arranged into facts, aggregates, and dimensions.  The schema can be formed by facts and dimensions together.
• Access Layer – In this layer, end-users works on data analysis by accessing the data through this layer.

Data Warehouse testing interview questions

Explain ETL Testing 

The testing is used to verify data that is extracted from different sources and destinations. 

• What are the responsibilities of the ETL Tester?

1. To verify the parts of ETL Data Warehouse.
2. To test ETL Software.
3. To perform the test in the backend. 
4. To pinpoint and solve issues. 
5. To create the design.
6. To perform the test harness and test cases. 
7. To approve design requirements and specifications.
8. To transfer from files (flat)

Tell the difference between Manual Testing and ETL Testing?

Manual Testing	ETL Testing
Tests the functionality of the program.	Tests the database.
Time consumer and slow process.	Time saver and gives a fast result.
Needs technical knowledge required to write test cases and scripts manually.	Automated, systematic tested process, doesn’t need technical knowledge.

What is data analytics?

Data analytics is an analysis of the raw data to make future decisions and conclusions based on the given data.

What does data purging mean?

Data purging means the method by which data can be removed permanently from the database. So, these are the most asked Data Warehouse Interview Questions which you should study for your interview. 

Conclusion

If you are interested in making a career in the Data Science domain, our 11-month in-person Postgraduate Certificate Diploma in Data Science course can help you immensely in becoming a successful Data Science professional. 

ALSO READ

• Data Science Roadmap – An Easy Guide For 2021